A light emitting diode (LED) is characterized by low power consumption, long lifespan, aesthetics, etc., based on remarkable improvement of its luminous efficiency. Thus, its market is rapidly expanding for applications as a backlight for liquid crystal displays (LCDs) or a special lighting field. Also, due to an additional improvement of luminous efficiency, as it is characterized by the low environmental load as described above, a huge market is expected to be formed in a general lighting field in the future.
Meanwhile, since the emission spectrum of an LED is dependent on a semiconductor material forming an LED chip, a phosphor suitable for each chip has to be installed on the LED chip so as to achieve white light for LCD backlights or general lightings. More particularly, a method of installing a yellow phosphor on an LED chip emitting blue light, a method of installing red and green phosphors on a blue LED chip, and also a method of installing red, green and blue phosphors on an LED chip emitting ultraviolet rays have been proposed. However, a method of installing a yellow phosphor on a blue LED and a method of installing red and green phosphors on a blue phosphor are currently the most widely used from the viewpoints of the luminous efficiency and cost of the LED chip.
As one method of installing a phosphor on an LED chip, a method of forming a film on a chip using a polymer composition in which a phosphor is dispersed and then sealing the film with a silicone-based material having high transparency and good thermal resistance and lightfastness has been performed.